1 Atomic structure & periodicity Flashcards
Define Isotope
Atoms of the same element with the same number of protons but a different number of neutrons.
Define 1st Ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous ions with a 1+ charge.
Define Mass Number
The total number of protons and neutrons in the nucleus.
Define Nuclear Charge
Total charge of all the protons in the nucleus.
Define Sub-shells
Electrons shells divided up into sub-shells (S,P,D,F) which have slightly different energy levels.
Define Orbitals
Sub-shells contain different numbers of orbitals which can each hold up to two electrons.
Define Relative Atomic Mass
The weighted average mean mass of all isotopes of an element relative to 1/12th the mass of an atom of C12.
How does atomic radius change across period 3?
How does First Ionisation energy change across period 3?
Radius: Decreases
Ionisation: Increases
Explanation:
Increased nuclear charge
Similar Shielding
Stronger attraction between valence electrons and nucleus.
Exceptions to 1st Ionisation energies in Period 3?
Sulphur:
1st P orbital to have 2 electrons.
Mutual repulsion
Less energy requires.
Aluminium:
Electrons removed from p orbital
Higher energy level
Less energy required.
How do successive ionisation energies change?
Increase:
each electron is harder to be removed than the previous.
Greater attraction to an already positive ion.
Rule for electron sub-shell stability? Elements that use this?
Half full or full d sub shells are more stable.
Cr and Cu use a 4s electron to get the half full/full d sub-shell.
What are the four stages of TOF?
Ionisation
Acceleration
Drift
Detection
What are the two types of ionisation?
Electrospray (adds proton +1 to mass)
Electron impact (removes electron)
What is acceleration TOF?
Positive ions are accelerated by an electric field and given the same KE.
What is drift TOF?
ions drift through a tube with no electric field, lighter ions move faster.
What is detection TOF?
Ions accept an electron at the positive plate, current proportional to abundance.
What is Electrospray ionisation TOF (Method)?
Sample dissolved in volatile solvent (Water/methanol)
Injected through fine hypodermic needle to fine mist.
Tip attached to + terminal of a high-voltage supply.
Ionised by gaining a proton as they leave the needle.
How to calculate Ar of a sample from abundance?
sum of mass x abundance/ total abundance
What does TOF calculate?
Mass and abundance
What rare occurrence can happen in TOF?
Ions produced with a 2+ charge will half the mass of the isotope on a Mass Spec.
What is the difference in properties of isotopes of the same element?
No difference as they have the same electron configuration.
Define atomic number?
Number of protons.
What are on the axes of a Mass Spec?
Relative Abundance (Y)
Mass/Charge (X)
What is Electron impact TOF (Method)?
High Speed Electrons fired from a hot wire filament knocks out an electron from orbit.
Explain the existence of isotopes.
Isotopes exist due to instability caused in an atom. (Radioactive decay).
How does melting point change across period 3?
Metallic elements MP increases (Na-Al):
More delocalisation of electrons per atom, Higher charge density, more energy required to overcome electrostatic forces.
Silicon MP is very high:
Giant covalent, lots of energy required to break strong cov bonds.
P,S,Cl,Ar MP are low:
Simple covalent, little energy required…
Of P,S,Cl,Ar:
S8 P4 Cl2 Ar,
IMF greater van der waals in larger molecules, requires more energy to overcome.
How to calculate isotope mass from abundance?
(isotope 1 x abundance) + (isotope 2 x abundance) / total abundance
Why is TOF in a vacuum
The whole TOF:MS is kept under this condition to prevent interference of foreign particles
